1. Field of the Invention
The present invention relates to a magnetic head for write and read of information on a magnetic recording medium such as a magnetic disc or magnetic tape.
2. Prior Art
There have hitherto been developed various kinds of magnetic heads for use in a magnetic disc type or magnetic tape type recording and reproducing device. As one of such magnetic heads is known a magnetic head, the core of which is at least in part composed of a laminate comprising magnetic metal thin layers and non-magnetic intermediate layers.
In this kind of magnetic head, the intermediate layer plays the role of magnetically isolating the magnetic metal thin layers from each other to diminish magnetic loss due to eddy current and prevent the lowering of magnetic recording and reproducing properties. As a material for the intermediate layer, silicon dioxide (SiO.sub.2) is normally used. The intermediate layer of SiO.sub.2 is required to have a thickness of at least 0.1 .mu.m in order to afford enough insulation. However, since this SiO.sub.2 intermediate layer is much harder than the magnetic metal thin layer made of an amorphous metal or permalloy, such intermediate layer can hardly be abraded.
In preparing a magnetic head using the above-mentioned laminate, the desired accuracy of fitting between the magnetic head and a magnetic recording medium should be obtained by abrading the fitting surface of the magnetic head. As is clear from the foregoing, there is a great difference in a rate of abrasion between the magnetic metal thin layer and the intermediate layer and, therefore, the abraded end of the intermediate layer projects beyond the abraded end of the magnetic metal thin layer. For this reason, the desired high accuracy of fitting cannot be obtained in prior art magnetic heads. Moreover, the magnetic metal thin layer is more fastly worn away than the intermediate layer during sliding of the magnetic disc or magnetic tape on the magnetic head. Therefore, the intermediate layer is in a state projected beyond the magnetic metal thin layer.
FIG. 1 shows the above-mentioned state. In FIG. 1, reference number 1 denotes a magnetic metal thin layer, 2 an intermediate layer, 3 a magnetic recording medium. As is seen from FIG. 1, the end of the intermediate layer 2 projects beyond the end of the magnetic metal thin layer 1 after finishing or during sliding of a recording medium on the magnetic head and, as a result, the magnetic recording medium 3 rises up in the vicinity of the intermediate layers 2.
Thus, the projected intermediate layers 2 injure the magnetic recording medium and, therefore, the durability of the magnetic recording medium is lowered. Moreover, the sufficient contact of the magnetic head and the magnetic recording medium cannot be achieved and, therefore, write or read of information are partially impossible to effect.
FIG. 2 schematically shows the state of the magnetic recording medium 3 into which information is partially not written. That is, FIG. 2 shows that on the magnetic medium there are present non-magnetized or weakly magnetized portions 4 and magnetized portions 5. The non-magnetized or weakly magnetized portions are formed in a stripe pattern on the magnetic recording medium 3 in a traveling direction thereof. The non-magnetized or weakly magnetized portions of the magnetic recording medium correspond to the portions forced to rise up due to the projected ends of the intermediate layers 2. Such formation of the non-magnetized or weakly magnetized portions should absolutely be avoided in order to obtain a high reliability of a magnetic recording device.